The present invention relates generally to chemical detector systems, and more specifically to systems using differential ion mobility spectroscopy.
Systems for the detection of airborne chemicals are commonly used to sense the presence of chemical warfare agents such as mustards and nerve agents. Such systems must be capable of accurately and reliably detecting and identifying dangerous chemicals in very low concentrations, and in a variety of environments. Man-portable versions of such systems are used by soldiers and engineers to identify possible hazards in the field.
Many fielded chemical warfare agent detectors use one variety or another of ion mobility spectroscopy (IMS). IMS-based detectors ionize incoming gases at an ionizer that feeds the ionized gases into an analyzer. Conventional devices include both time-of-flight based IMS analyzers, and differential ion mobility spectroscopy (DMS) analyzers. Field asymmetric ion mobility spectroscopy (FAIMS) devices are DMS systems that utilize analyzers with asymmetric radio frequency fields to selectively pass ions of particular volume and charge to a reception element such as a biased Faraday collector. Recently developed rapid thermal IMS (RTIMS) systems utilize DMS techniques with micro-scale analyzer structures, allowing RTIMS instruments to achieve stronger fields.
IMS systems have low tolerances for humidity. To remove water from sample air, many fielded DMS systems use dehumidification loops whereby inlet air is mixed with dry air and recirculated through or past one or more consumable ceramic sorbent or chemical desiccant elements. Recirculation systems are power intensive, and desiccant elements may need to be replaced often in high-humidity environments.